Bragg reflection structure (i.e. Distributed Bragg Reflector, DBR) is formed generally by alternately stacking high-refractive index material layers and low-refractive index material layers. It is required that the material should not absorb visible light. A DBR for improving light-emitting efficiency of semiconductor microcavity light-emitting diode is described in Chinese Paten Application CN 101478025A.
In the technical field of display, liquid crystal display dependent on normal light-emitting diode (LED) backlight has been used widely. In addition, Organic Light-Emitting Diode (OLED) device is paid more and more attention due to its advantages of uniform luminance, flicker free, sufficient safeness for environment, and so on. However, both of normal LED and OLED have lower light-emitting efficiency. For example, owing to influences of absorption, loss, interface scattering and reflection, light-emitting efficiency of OLED is only about 20%. Thus, it is an important research subject in the display technical field to improve light-emitting efficiency.